Metal-Free Hydrazinium Halide Perovskitoid Single Crystals for X-ray Detection

Metal-free perovskitoids (MFPs) with N₂H₅⁺ as B-site component possess higher crystal density and hydrogen bonding networks and have been recently expanded into X-ray detection. However, research on this material is in its infancy and lacks an understanding of the function of halide components on physical properties and device performance. Here, N₂H₅-based MFP single crystals (SCs) with different halides are fabricated, and the influence of halides on the crystal structure, band nature, charge transport characteristics, and final device performance is actively explored. Based on theory and experiments, the tolerance factor and octahedral factor jointly determine the octahedral composition. Further, halides with different electronegativities and ionic radii also affect octahedral distortion and energy band bending, further influencing carrier transport and device performance. Finally, a sensitivity of 1284 μC Gy_air^-1 cm^-2 and low detection limits (LoD) of 5.62 μGy_air s^-1 were obtained by the Br-based device due to its superior physical properties.